Optical reduction system with elimination of reticle diffraction induced bias

ABSTRACT

An optical reduction system for use in the photolithographic manufacture of semiconductor devices having one or more quarter-wave plates operating near the long conjugate end. A quarter-wave plate after the reticle provides linearly polarized light at or near the beamsplitter. A quarter-wave plate before the reticle provides circularly polarized or generally unpolarized light at or near the reticle. Additional quarter-wave plates are used to further reduce transmission loss and asymmetries from feature orientation. The optical reduction system provides a relatively high numerical aperture of 0.7 capable of patterning features smaller than 0.25 microns over a 26 mm×5 mm field. The optical reduction system is thereby well adapted to a step and scan microlithographic exposure tool as used in semiconductor manufacturing. Several other embodiments combine elements of different refracting power to widen the spectral bandwidth which can be achieved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to optical systems used insemiconductor manufacturing.

[0003] 2. Background Art

[0004] Semiconductor devices are typically manufactured using variousphotolithographic techniques. The circuitry used in a semiconductor chipis projected from a reticle onto a wafer. This projection is oftenaccomplished with the use of optical systems. The design of theseoptical systems is often complex, and it is difficult to obtain thedesired resolution necessary for reproducing the ever-decreasing size ofcomponents being placed on a semiconductor chip. Therefore, there hasbeen much effort expended to develop an optical reduction system capableof reproducing very fine component features, less than 0.25 microns. Theneed to develop an optical system capable of reproducing very finecomponent features requires the improvement of system performance.

[0005] A conventional optical system is disclosed in U.S. Pat. No.5,537,260 entitled “Catadioptric Optical Reduction System with HighNumerical Aperture” issued Jul. 16, 1996 to Williamson, which isincorporated by reference herein in its entirety. This referencedescribes an optical reduction system having a numerical aperture of0.35. Another optical system is described in U.S. Pat. No. 4,953,960entitled “Optical Reduction System” issuing Sep. 4, 1990 to Williamson,which is incorporated by reference herein in its entirety. Thisreference describes an optical system operating in the range of 248nanometers and having a numerical aperture of 0.45.

BRIEF SUMMARY OF THE INVENTION

[0006] While these optical systems perform adequately for their intendedpurpose, there is an ever increasing need to improve system performance.The present inventor has identified that a need exists for eliminatingdiffraction induced by bias at the reticle. Further, there is a need foran optical system having low reticle diffraction capable of acceptablesystem performance over a large spectral waveband.

[0007] Reticle diffraction induced by results from the way linearlypolarized light interacts with the features of the reticle. The featureorientation of the reticle is determined by the semiconductor devicebeing projected. Since there is an increasing need to reduce the size ofsemiconductor devices and feature orientation is dictated by theapplication of the semiconductor device, the present inventor focused ontreating reticle diffraction.

[0008] Linearly polarized light is typically used in certainphotolithographic projection optic systems. Diffraction results from theinteraction of light and the features on the reticle. Linearly polarizedlight travels through the reticle differently depending on theorientation of its features. Asymmetries result from this interaction.The asymmetries or print biases are then projected through the opticalsystem onto the wafer. Print bias is significant enough to alter thethickness of the lines projected on the wafer. Variations on the waferaffect the performance of the semiconductor device, and in some casesprevent the device from performing to required specifications.

[0009] The use of circularly polarized light at the reticle caneliminate the asymmetries which result from feature orientation. Thiscircularly polarized light is indistinguishable from unpolarized lightin its imaging behavior. The imaging behavior of unpolarized light issuch that it diffracts equally regardless of the orientation of thefeature through which it is projected. Thus the print biases are reducedthroughout the optical system.

[0010] However, other factors, such as transmission loss, prevent theuse of circularly polarized light throughout an optical system. Thus,the present invention involves the use of phase shifters, which can takethe form of wave plates, retardation plates and the like, to selectivelyalter the polarization of the light before the reticle and opticalsystem.

[0011] In one embodiment, the present invention is a catadioptricoptical reduction system for use in the photolithographic manufacture ofsemiconductor devices having one or more quarter-wave plates operatingnear the long conjugate end. A quarter-wave plate after the reticleprovides linearly polarized light at or near the beamsplitter. Aquarter-wave plate before the reticle provides circularly polarized orgenerally unpolarized light at or near the reticle. Additionalquarter-wave plates are used to further reduce transmission loss andasymmetries from feature orientation. The catadioptric optical reductionsystem provides a relatively high numerical aperture of 0.7 capable ofpatterning features smaller than 0.25 microns over a 26 mm×5 mm field.The optical reduction system is thereby well adapted to a step and scanmicrolithographic exposure tool as used in semiconductor manufacturing.Several other embodiments combine elements of different refracting powerto widen the spectral bandwidth which can be achieved.

[0012] In another embodiment, the present invention is a catadioptricreduction system having, from the object or long conjugate end to thereduced image or short conjugate end, an first quarter-wave plate, areticle, a second quarter-wave plate, a first lens group, a second lensgroup, a beamsplitter cube, a concentric concave mirror, and a thirdlens group. The first quarter-wave plate operates to circularly polarizethe radiation passed to the reticle. The second quarter-wave plateoperates to linearly polarize the radiation after the reticle before thefirst lens group. The concave mirror operates near unit magnification.This reduces the aberrations introduced by the mirror and the diameterof radiation entering the beamsplitter cube. The first and second lensgroups before the concave mirror provide enough power to image theentrance pupil at infinity at the aperture stop at or near the concavemirror. The third lens group after the concave mirror provides asubstantial portion of the reduction from object to image of the opticalsystem, as well as projecting the aperture stop to an infinite exitpupil. High-order aberrations are reduced by using an aspheric concavemirror.

[0013] Further embodiments, features, and advantages of the presentinvention, as well as the structure and operation of the variousembodiments of the present invention, are described in detail below withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0014] The accompanying drawings, which are incorporated herein and forma part of the specification, illustrate the present invention and,together with the description, further serve to explain the principlesof the invention and to enable a person skilled in the pertinent art tomake and use the invention. In the drawings:

[0015]FIG. 1 is a schematic illustration of a conventional opticalprojection system.

[0016]FIG. 2A is an illustration of diffraction at the reticle.

[0017]FIG. 2B is an illustration of the properties of a quarter-waveplate.

[0018]FIG. 2C is an illustration of the properties of a half waveplate.

[0019]FIG. 3 is a schematic illustration of the present invention usingmore than two quarter-wave plates.

[0020]FIG. 4 is a schematic illustration of an alternative embodiment.

[0021]FIG. 5 is a schematic illustration of one embodiment of thepresent invention using a single refracting material.

[0022]FIG. 6 is another embodiment of the present invention using twodifferent refracting materials.

[0023]FIG. 7 is another embodiment of the present invention using morethan two different refracting materials.

[0024]FIG. 8 is another embodiment of the present invention.

[0025]FIG. 9 is yet a further embodiment of the present invention.

[0026] The present invention will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers indicateidentical or functionally similar elements. Additionally, the left-mostdigit(s) of a reference number identifies the drawing in which thereference number first appears.

DETAILED DESCRIPTION OF THE INVENTION

[0027] I. Overview

[0028] A. Conventional Optical System

[0029] B. Reticle Diffraction

[0030] C. Polarization and Wave Plates

[0031] II. Terminology

[0032] III. Example Implementations

[0033] A. Optical System With Elimination of Reticle Diffraction InducedBias

[0034] B. Alternate Embodiment

[0035] C. Further Embodiments

[0036] IV. Alternate Implementation

[0037] I. Overview

[0038] A. Conventional Optical System

[0039]FIG. 1 illustrates a conventional optical reduction system. Fromits long conjugate end where the reticle is placed to its shortconjugate end where the wafer is placed, it possesses a first opticalcomponent group 120, a beamsplitter cube 150, a first quarter-wave plate140, a concave mirror 130, a second quarter-wave plate 160, and a secondoptical component group 170. A feature of any optical system is theinterdependence of numerical aperture size and spectral radiationrequirements. In order to efficiently illuminate the image or waferplane 180, linearly polarized light is used. The limitations of linearlypolarized light are introduced above and discussed in the followingsections.

[0040] B. Reticle Diffraction Induced Bias

[0041] As recognized by the present inventor, the use of linearlypolarized light at numerical apertures greater than about 0.5 introducessmall, but noticeable, asymmetries in the imaging. These asymmetries inimaging are caused at least in part by diffraction of the linearlypolarized light at certain feature orientations. FIG. 2A illustrates theasymmetries or print biases which result from the use of linearlypolarized light at the reticle 110. Simply, reticle 110 is placed in thepath of both linearly polarized light 205 and circularly polarized light210. The two types of light are separated by separator 215. After thereticle, the intensity of the light is distributed differently, as shownby distribution curves 220 and 225. The results are shown on wafer 180.Here, the projected image 230 resulting from the use of linearlypolarized light 205 is not as clear or sharp as projected image 235which results from the use of circularly polarized light 210.

[0042] Circularly polarized light 210 is indistinguishable fromunpolarized light in its imaging behavior. The imaging behavior ofunpolarized light is such that it diffracts equally regardless of theorientation of the feature through which it is projected. When theprojection optic cannot accept unpolarized light, but requires linearlypolarized light, it is possible to provide circularly polarized light toilluminate the reticle and thereby eliminate the feature orientationbias. Thus, print biases are reduced.

[0043] C. Polarization and Wave Plates

[0044] The properties of wave plates are shown in FIGS. 2B and 2C. FIG.2B illustrates the properties of a quarter-wave plate. Linearlypolarized input 240 enters the wave plate 245 at the input polarizationplane 255. The optic axis 250 and other factors discussed in detailbelow determine the orientation of the output light. Here, wave plate245 is designed to produce circularly polarized output 260.

[0045] Similarly, FIG. 2C illustrates the properties of a half-waveplate. Linearly polarized input 265 enters the wave plate 270 at theinput polarization plane 280. The optic axis 275 and other factorsdiscussed in detail below determine the orientation of the output light.Here, wave plate 270 is designed to produce linearly polarized withplane of polarization retarded output 285.

[0046] Wave plates (retardation plates or phase shifters) are made frommaterials which exhibit birefringence. Birefringent materials, such ascrystals, are generally anisotropic. This means that the atomic bindingforces on the electron clouds are different in different directions andas a result so are the refractive indices.

[0047] In the case of uniaxial birefringent crystals, a single symmetryaxis (actually a direction) known as the optic axis (shown in FIGS. 2Band 2C as elements 250 and 275, respectively) displays two distinctprincipal indices of refraction: the maximum index n_(o) (the slow axis)and the minimum index n_(e) (the fast axis). These two indicescorrespond to light field oscillations parallel and perpendicular to theoptic axis.

[0048] The maximum index results in ordinary rays passing through thematerial. The minimum index results in extraordinary rays passingthrough the material. The velocities of the extraordinary and ordinaryrays through the birefringent materials vary intensely with theirrefractive indices. The difference in velocities gives rise to a phasedifference when the two beams recombine. In the case of an incidentlinearly polarized beam this is given by:${\alpha = {2\pi \quad d\frac{\left( {n_{e} - n_{o}} \right)}{\lambda}}};$

[0049] where α is the phase difference; d is the thickness of waveplate; n_(e), n_(o) are the refractive indices of the extraordinary andordinary rays respectively, and λ is the wavelength. Thus, at anyspecific wavelength the phase difference is governed by the thickness ofthe wave plate.

[0050] As discussed above, FIG. 2B illustrates the operation of aquarter-wave plate. The thickness of the quarter-wave plate is such thatthe phase difference is ¼-wavelength (zero order) or some multiple of ¼wavelength (multiple order). If the angle between the electric fieldvector of the incident linearly polarized beam and the retarderprincipal plane of the quarter-wave plate is 45 degrees, the emergentbeam is circularly polarized.

[0051] Additionally, when a quarter-wave plate is double passed, e.g.,when the light passes through it twice because it is reflected off amirror, it acts as a half-wave plate.

[0052] By quarter-wave plate is meant a thickness of birefringentmaterial which introduces a quarter of a wavelength of the incidentlight. This is in contrast to an integral number of half plusquarter-waves or two thicknesses of material whose phase retardancediffers by a quarter-wave. The deleterious effects of large angle ofincidence variations are thereby minimized at the high numericalaperture by the use of such zero order wave plates, and by restrictingthe field size in the plane of incidence.

[0053] Similarly, FIG. 2C illustrates the operation of a half-waveplate. The thickness of a half-wave plate is such that the phasedifference is ½-wavelength (zero order) or some odd multiple of½-wavelength (multiple order). A linearly polarized beam incident on ahalf-wave plate emerges as a linearly polarized beam but rotated suchthat its angle to the optical axis is twice that of the incident beam.

[0054] II. Terminology

[0055] To more clearly delineate the present invention, an effort ismade throughout the specification to adhere to the following termdefinitions as consistently as possible.

[0056] The term “circuitry” refers to the features designed for use in asemiconductor device.

[0057] The term “feature orientation” refers to the patterns printed ona reticle to projection.

[0058] The term “long conjugate end” refers to the plane at the objector reticle end of the optical system.

[0059] The term “print bias” refers to the variations in the lines onthe wafer produced by asymmetries in the optical system. Asymmetries areproduced by diffraction at various stages of the system and the reticle.

[0060] The term “semiconductor” refers to a solid state substance thatcan be electrically altered.

[0061] The term “semiconductor chip” refers to semiconductor devicepossessing any number of transistors or other components.

[0062] The term “semiconductor device” refers to electronic equipmentpossessing semiconductor chips or other elements.

[0063] The term “short conjugate end” refers to the plane at the imageor wafer end of the optical system.

[0064] The term “wave plate” refers to retardation plates or phaseshifters made from materials which exhibit birefringence.

[0065] III. Example Implementations

[0066] A. Optical System with Elimination of Reticle Diffraction InducedBias

[0067] The present invention uses circularly polarized light toeliminate the reticle diffraction induced biases of conventionalsystems. FIG. 3 illustrates an embodiment of the present invention thateliminates such asymmetries or print biases. A first quarter-wave plate305 is introduced before the object or reticle plane 110. Firstquarter-wave plate 305 converts the linearly polarized light intocircularly polarized light, as illustrated in FIG. 2B. As discussedabove, circularly polarized light is indistinguishable from unpolarizedlight in its imaging behavior. The imaging behavior of unpolarized lightis such that it diffracts equally regardless of the orientation of thefeature through which it is projected. Thus the print biases whichresult from reticle diffraction are reduced.

[0068] In order to minimize transmission loss through the rest of theoptical system, second quarter-wave plate 315 is inserted to linearlypolarize the radiation before the optical component group 320.

[0069] With respect to quarter-wave plates 305, 315, 340 and 360, oneorientation is to have the first quarter-wave plate 305 oriented withits fast axis parallel to that of the input light. The secondquarter-wave plate 315 and fourth quarter-wave plate 360 have their fastaxes in a parallel orientation but perpendicular to the fast axis ofthird quarter-wave plate 340.

[0070] B. Alternate Embodiment

[0071] It is also apparent to one skilled in the relevant art thatsecond quarter-wave plate 315 could be inserted into the system anywherebefore the beamsplitter 350. This aspect is shown in FIG. 4 where secondquarter-wave plate 425 serves the same function. The transmission losscaused by the use of circularly polarized light within optical componentgroup 320 influences the placement of second quarter-wave plate 425.

[0072] Specifically, the use of unpolarized or circularly polarizedlight at the beamsplitter would cause a transmission loss of 50%. If anon-polarized beamsplitter were to be used, 75% of the light would belost. Therefore, while alternate embodiments are possible, they may notbe feasibly implemented.

[0073] With respect to quarter-wave plates 405, 425, 440 and 460, oneorientation is to have the first quarter-wave plate 405 oriented withits fast axis parallel to that of the input light. The secondquarter-wave plate 425 and fourth quarter-wave plate 460 have their fastaxes in a parallel orientation but perpendicular to the fast axis ofthird quarter-wave plate 440.

[0074] C. Further Embodiments

[0075] The present invention can be implemented in various projectionoptic systems. For example, the present invention can be implemented incatadioptric systems as described in detail herein, as well asrefractive and reflective systems. On skilled in the relevant art, basedat least on the teachings provided herein, would recognize that theembodiments of the present invention are applicable to other reductionsystems. More detailed embodiments of the present invention as providedbelow.

[0076]FIG. 5 illustrates one embodiment of the optical reduction systemof the present invention. From its long conjugate end, it comprises anfirst quarter-wave plate 508, an object or reticle plane 110, a secondquarter-wave plate 511, a first lens group LG1, a folding mirror 520, asecond lens group LG2, a beamsplitter cube 530, a third quarter-waveplate 532, a concave mirror 534, a second quarter-wave plate 538, and athird lens group LG3. The image is formed at image or wafer plane 180.The first lens group LG1 comprises a shell 512, a spaced doubletincluding positive lens 514 and negative lens 516, and positive lens518. The shell 512 is an almost zero power or zero power lens. Thesecond lens group LG2 comprises a positive lens 522, a spaced doubletincluding a negative lens 524 and a positive lens 526, and negative lens528. The third lens group LG3 comprises two positive lenses 540 and 542,which are strongly positive, shell 544, and two positive lenses 546 and548, which are weakly positive. The first quarter-wave plate 508 passescircularly polarized light incident upon the object or reticle plane110. The folding mirror 520 is not essential to the operation of thepresent invention. However, the folding mirror permits the object andimage planes to be parallel which is convenient for one intendedapplication of the optical system of the present invention, which is themanufacture of semiconductor devices using photolithography with a stepand scan system.

[0077] Radiation enters the system at the long conjugate end and passesthrough the first lens group LG1, is reflected by the folding mirror520, and passes through the second lens group LG2. The radiation entersthe beamsplitter cube 530 and is reflected from surface 536 passingthrough quarter-wave plate 532 and reflected by concave mirror 534. Theradiation then passes back through the quarter-wave plate 532, thebeamsplitter cube 530, the quarter-wave plate 538, lens group LG3, andis focused at the image or wafer plane 180.

[0078] Lens groups upstream of the mirror, LG1 and LG2, provide onlyenough power to image the entrance pupil at infinity to the aperturestop 531 at or near the concave mirror 534. The combined power of lensgroups LG1 and LG2 is slightly negative. The shell 512 and air spaceddoublet 514 and 516 assist in aberration corrections includingastigmatism, field curvature, and distortion. The lens group LG3, afterthe concave mirror 534, provides most of the reduction from object toimage size, as well as projecting the aperture stop to an infinite exitpupil. The two strongly positive lenses 540 and 542 provide a highnumerical aperture at the image and exit pupils and infinity. The shell544 has almost no power. The two weakly positive lenses 546 and 548 helpcorrect high order aberrations. The concave mirror 534 may provide areduction ratio of between 1.6 and 2.7 times that of the total system.

[0079] The negative lens 524 in the second lens group LG2 provides astrongly diverging beam directed at the beamsplitter cube 530 andconcave mirror 534. The strongly positive lens 522 provides lateralcolor correction. The air space doublet comprising lenses 524 and 526helps to correct spherical aberrations and coma. Concave mirror 534 ispreferably aspheric, therefore helping further reduce high orderaberrations.

[0080] The transmission losses introduced by the beamsplitter cube 530are minimized by illuminating the object or reticle with linearlypolarized light and including a quarter-wave plate 532 between thebeamsplitter cube 530 and the concave mirror 534. Additionally, byincreasing the numerical aperture in lens group LG3, after the concavemirror 534 and beamsplitter cube 530, the greatest angular range is notseen in these elements.

[0081] However, the use of linearly polarized light at numericalapertures greater than about 0.5 introduces small but noticeableasymmetries in the imaging. In the present invention, this caneffectively be removed by introducing another quarter-wave plate 538after the final passage through the beamsplitter cube 530, therebyconverting the linearly polarized light into circularly polarized light.This circularly polarized light is basically indistinguishable fromunpolarized light in its imaging behavior.

[0082] The optical system illustrated in FIG. 5 is designed to operateat a reduction ratio of 4 to 1. Therefore, the numerical aperture in theimage space is reduced from 0.7 by a factor of 4 to 0.175 at the objector reticle plane 110. In other words, the object space numericalaperture is 0.175 and the image space numerical aperture is 0.7. Uponleaving the first lens group LG1 the numerical aperture is reduced to0.12, a consequence of the positive power needed in lens group LG1 toimage the entrance pupil at infinity to the aperture stop of the systemclose to the concave mirror 534. The numerical aperture after leavingthe second lens group LG2 and entering the beamsplitter is 0.19.Therefore, the emerging numerical aperture from the second lens groupLG2, which is 0.19, is larger than the entering or object spacenumerical aperture of lens group LG1, which is 0.175. In other words,the second lens group LG2 has an emerging numerical aperture greaterthan the entering numerical aperture of the first lens group LG1. Thisis very similar to the object space numerical aperture, which is 0.175,due to the overall negative power of the second lens group LG2. This iscontrary to prior art systems where the numerical aperture entering abeamsplitter cube is typically close to zero or almost collimated. Theconcave mirror 534 being almost concentric, the numerical aperture ofthe radiation reflected from it is increased only slightly from 0.19 to0.35. The third lens group LG3 effectively doubles the numericalaperture to its final value of 0.7 at the wafer or image plane 180.

[0083] The present invention achieves its relatively high numericalaperture without obstruction by the edges of the beamsplitter cube bymeans of the negative second group LG2 and the strongly positive thirdlens group LG3. The use of the beamsplitter cube 530 rather than a platebeamsplitter is important in the present invention because at numericalapertures greater than about 0.45 a beamsplitter cube will providebetter performance. There is a reduction of the numerical aperturewithin the cube by the refractive index of the glass, as well as theabsence of aberrations that would be introduced by a tilted platebeamsplitter in the non-collimated beam entering the beamsplitter. Theconstruction data for the lens system illustrated in FIG. 5 according tothe present invention is given in Table 1 below. TABLE 1 Radius ofCurvature Element (mm) Thickness Aperture Diameter (mm) Number FrontBack (mm) Front Back Glass 508 Infinite Infinite 4.500 123.0000 123.0000Silica Space 0.7500 110 Infinite 63.3853 Space 0.7500 511 InfiniteInfinite 4.500 123.0000 123.0000 Silica Space 0.7500 512 −158.7745−177.8880 15.0000 124.0478 131.7725 Silica Space 36.1130 514 −556.6911−202.0072 22.2126 148.3881 152.5669 Silica Space 38.7188 516 −183.7199−558.8803 15.0000 156.5546 166.5750 Silica Space 10.0674 518 427.2527−612.2450 28.8010 177.4010 179.0292 Silica Space 132.3320 520 Infinite−74.0000 184.6402 Reflection 522 −240.4810 2050.9592 −33.3135 188.4055185.3395 Silica Space −29.3434 524 421.7829 −145.6176 −12.0000 175.5823169.0234 Silica Space −4.2326 526 −150.4759 472.0653 −46.5091 171.4244169.9587 Silica Space −2.0000 528 −1472.2790 −138.2223 −15.0000 165.3586154.8084 Silica Space −27.2060 530 Infinite Infinite −91.8186 155.6662253.0917 Silica 536 Infinite 253.0917 Reflection 530 Infinite Infinite91.8186 253.0917 253.0917 Silica Space 2.0000 532 Infinite Infinite6.0000 185.8693 186.8401 Silica Space 17.9918 Stop 188.0655 534 Aspheric−17.9918 188.0655 Reflection 532 Infinite Infinite −6.0000 183.5471180.1419 Silica Space −2.0000 530 Infinite Infinite −91.8186 178.3346149.2832 Silica 530 Infinite Infinite −70.000 149.2832 128.8604 SilicaSpace −2.0000 538 Infinite Infinite −4.500 127.9681 126.6552 SilicaSpace −0.7500 540 −175.1330 1737.4442 −17.7754 121.4715 118.2689 SilicaSpace −0.7500 542 −108.8178 −580.1370 −18.2407 104.5228 97.7967 SilicaSpace −0.7500 544 −202.2637 −86.6025 −31.1216 91.7061 57.4968 SilicaSpace −2.3507 546 −122.1235 −488.7122 −17.9476 56.4818 41.1675 SilicaSpace −0.2000 548 −160.8506 −360.1907 −6.1500 39.4528 33.5764 SilicaSpace −4.000 180 Infinite 26.5019

[0084] Concave mirror 534 has an aspheric reflective surface accordingto the following equation:${Z = {\frac{({CURV})Y^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)({CURV})^{2}Y^{2}}}} + {(A)Y^{4}} + {(B)Y^{6}} + {(D)Y^{10}} + {(E)Y^{12}} + {(F)Y^{14}}}};$

[0085] wherein the constants are as follows:

[0086] CURV=−0.00289051

[0087] K=0.000000

[0088] A=6.08975×10⁻¹¹

[0089] B=2.64378×10¹⁴

[0090] C=9.82237×10⁻¹⁹

[0091] D=7.98056×10⁻²³

[0092] E=−5.96805×10⁻²⁷

[0093] F=4.85179×10⁻³¹

[0094] The lens according to the construction in Table 1 is optimizedfor radiation centered on 248.4 nanometers. The single refractingmaterial of fused silica and the large portion of refracting powerrestricts the spectral bandwidth of the embodiment illustrated in FIG. 5to about 10 picometers or 0.01 nanometers. This spectral bandwidth ismore than adequate for a line narrowed krypton fluoride excimer laserlight source. The embodiment illustrated in FIG. 5 can be optimized forany wavelength for which fused silica transmits adequately.

[0095] A wider spectral bandwidth can be achieved by the use of twooptical materials with different dispersions. A second embodiment of thepresent invention is illustrated in FIG. 6. From its long conjugate end,it comprises a first quarter-wave plate 608, an object or reticle plane110, a second quarter-wave plate 611, a lens group LG4, a folding mirror622, a lens group LG5, a beamsplitter cube 632 having surface 638, athird quarter-wave plate 634, a concave mirror 636, a fourthquarter-wave plate 640, and lens group LG6. The image is formed at imageor wafer plane 180. The lens group LG4 comprises a spaced doubletincluding negative lens 612 and positive lens 614, a weak positive lens616, positive lens 618, and shell 620. The lens group LG5 comprises apositive lens 624, a negative lens 626, a positive lens 628, and anegative lens 630. The lens group LG6 comprises two positive lenses 642,cemented doublet including positive lens 644 and negative lens 646,positive lens 648, and cemented doublet including shell 650 and positivelens 652.

[0096] This second embodiment uses calcium fluoride in one of theindividual positive lenses of the lens group LG4, negative lenses of thelens group LG5, and two of the positive lenses of the lens group LG6.The construction data of the second embodiment illustrated in FIG. 6 ofthe present invention is given in Table 2 below. TABLE 2 Radius ofCurvature Element (mm) Thickness Aperture Diameter (mm) Number FrontBack (mm) Front Back Glass 608 Infinite Infinite 4.5000 123.0000123.0000 Silica Space 0.5000 110 Infinite 60.4852 Space 0.5000 611Infinite Infinite 4.5000 123.0000 123.0000 Silica 612 −205.5158 539.179115.2158 124.0926 137.3346 Silica Space 8.8054 614 2080.9700 −210.653932.4984 142.6149 151.7878 Silica Space 1.2676 616 310.4463 700.374840.7304 162.4908 165.2126 CaFl Space 0.5000 618 634.1820 −798.852327.5892 165.4595 166.4747 Silica Space 0.5000 620 1480.0597 1312.124725.4322 168.7516 164.7651 Silica Space 136.2343 622 Infinite −74.0000161.9590 Reflection 624 −761.9176 1088.9351 −19.2150 160.3165 159.2384Silica Space −19.9465 626 648.8361 −202.5872 −12.0000 155.1711 153.0635CaFl Space −7.6304 628 −400.4276 458.5060 −25.8769 153.0635 153.8055Silica Space −2.0000 630 −818.0922 −168.5034 −27.5927 152.6663 147.5200CaFl Space −20.5014 632 Infinite Infinite −91.7553 148.6158 252.7349Silica 638 Infinite 252.7349 Reflection 632 Infinite Infinite 91.7553252.7349 252.7349 Silica Space 2.0000 634 Infinite Infinite 6.0000185.8070 187.0026 Silica Space 18.1636 Stop 188.5681 636 Aspheric−18.1636 188.5681 Reflection 634 Infinite Infinite −6.0000 184.2566181.1084 Silica Space −2.0000 632 Infinite Infinite −91.7553 179.3838151.7747 Silica 632 Infinite Infinite −70.0000 151.7747 133.3985 SilicaSpace −2.0000 640 Infinite Infinite −4.5000 132.5690 131.3876 SilicaSpace −0.5000 642 −112.0665 −597.6805 −21.4866 123.4895 119.2442 SilicaSpace −0.5000 644 −116.3137 282.3140 −24.0940 107.8451 101.2412 CaFl 646282.3140 −66.5293 −13.7306 101.2412 72.6862 Silica Space −2.6346 648−77.2627 −374.4800 −17.9594 72.0749 62.7659 Silica Space −0.5452 650−130.1381 −57.1295 −20.8147 58.9696 37.4889 Silica 652 −57.1295−7305.8777 −6.1425 37.4889 34.3156 CaFl Space −4.0000 180 Infinite26.4992

[0097] wherein the constants for the aspheric mirror 634 used in theequation after Table 1 are as follows:

[0098] CURV=−0.00286744

[0099] K=0.000000

[0100] A=−1.92013×10⁻⁰⁹

[0101] B=−3.50840×10⁻¹⁴

[0102] C=2.95934×10⁻¹⁹

[0103] D=−1.10495×10⁻²²

[0104] E=9.03439×10⁻²⁷

[0105] F=−1.39494×10⁻³¹

[0106] This second embodiment is optimized for radiation centered on193.3 nanometers and has a spectral bandwidth of about 200 picometers or0.2 nanometers. A slightly line narrowed argon fluoride excimer laser isan adequate light source. Additionally, the design can be optimized forany wavelength for which both refractive materials transmit adequately.The bandwidth will generally increase for longer wavelengths, as thematerial dispersions decrease. For example, around 248.4 nanometers sucha two-material design will operate over at least a 400 picometers, 0.4nanometers bandwidth.

[0107] At wavelengths longer than 360 nanometers, a wider range ofoptical glasses begin to have adequate transmission. A third embodimentillustrated in FIG. 7 takes advantage of this wider selection of glassesand further reduced dispersion. From its long conjugate end, itcomprises a first quarter-wave plate 708, an object or reticle plane110, a second quarter-wave plate 711, a lens group LG7, a folding mirror722, a lens group LG8, a beamsplitter cube 732 having a surface 738, athird quarter-wave plate 734, a concave mirror 736, a fourthquarter-wave plate 740, and lens group LG9. The image is formed at imageor wafer plane 180. The lens group LG7 comprises a spaced doubletcomprising negative lens 712 and positive lens 714, spaced doubletincluding positive lens 716 and negative lens 718, and positive lens720. The lens group LG8 comprises a positive lens 724, a negative lens726, a positive lens 728, and a negative lens 730. The lens group LG9comprises a positive lenses 742, cemented doublet including positivelens 744 and negative lens 746, positive lens 748, and cemented doubletincluding shell 750 and positive lens 752.

[0108] The construction data of the third embodiment illustrated in FIG.7 is given in Table 3 below. TABLE 3 Radius of Curvature Element (mm)Thickness Aperture Diameter (mm) Number Front Back (mm) Front Back Glass708 Infinite Infinite 4.5000 125.0000 125.0000 Silica Space 0.5000 110Infinite 59.2960 Space 0.5000 711 Infinite Infinite 4.5000 125.0000125.0000 Silica 712 −620.7809 361.8305 20.2974 125.9406 134.7227 PBM2YSpace 2.6174 714 515.7935 −455.1015 39.8858 135.3384 145.6015 PBM2YSpace 14.7197 716 431.3189 −239.4002 36.9329 155.6269 157.3014 BSL7YSpace 0.5000 718 −259.6013 685.3286 26.3534 156.9363 162.2451 PBM2YSpace 1.4303 720 361.5709 −1853.2955 23.3934 168.7516 165.1801 BAL15YSpace 131.8538 722 Infinite −77.8469 169.9390 Reflection 724 −429.2950455.4247 −32.3086 173.0235 171.1102 PBL6Y Space −27.6206 726 401.0363−180.0031 −12.0000 159.3555 154.7155 BSL7Y Space −5.6227 728 −258.47221301.3764 −26.1321 154.7155 154.1517 PBM8Y Space −2.0000 730 −1282.8931−180.2226 −12.0000 153.1461 149.4794 BSL7Y Space −19.7282 732 InfiniteInfinite −91.7349 150.4585 252.6772 Silica 738 Infinite 252.6772Reflection 732 Infinite Infinite 91.7349 252.6772 252.6772 Silica Space2.0000 734 Infinite Infinite 6.0000 185.6435 186.7758 Silica Space18.2715 Stop 188.1745 736 Aspheric −18.2715 188.1745 Reflection 734Infinite Infinite −6.0000 183.6393 180.1377 Silica Space −2.0000 732Infinite Infinite −91.7349 178.3236 147.9888 Silica 732 InfiniteInfinite −70.0000 147.9888 126.9282 Silica Space −2.000 740 InfiniteInfinite −4.5000 126.0289 124.6750 Silica Space −0.5000 742 −119.8912−610.6840 −18.6508 117.5305 113.4233 BSM51Y Space −0.5000 744 −114.1327384.9135 −21.1139 102.6172 96.4137 BSL7Y 746 384.9135 −70.2077 −13.057696.4137 71.1691 PBL26Y Space −2.8552 748 −85.7858 −400.3240 −16.914770.5182 61.2633 BSM51Y Space −0.8180 750 −151.5235 −54.0114 −19.581057.6234 37.3909 BSM51Y 752 −54.0114 −2011.1057 −6.3947 37.3909 34.2119PBL6Y Space −4.0000 180 Infinite 26.5002

[0109] wherein the constants for the aspheric mirror 736 used in theequation after Table 1 as follows:

[0110] CURV=−0.00291648

[0111] K=0.000000

[0112] A=−1.27285×10⁻⁹

[0113] B=−1.92865×10⁻¹⁴

[0114] C=6.21813×10⁻¹⁹

[0115] D=−6.80975×10²³

[0116] E=6.04233×10⁻²⁷

[0117] F=3.64479×10⁻³²

[0118] This third embodiment operates over a spectral bandwidth of 8nanometers centered on 365.5 nanometers. A radiation of this spectralbandwidth can be provided by a filtered mercury arc lamp at the I-linewaveband. The optical glasses other than fused silica used in this thirdembodiment are commonly known as I-line glasses. These optical glasseshave the least absorption or solarization effects at the mercury I-linewavelength.

[0119]FIG. 8 illustrates a fourth embodiment of the optical reductionsystem of the present invention. This embodiment has a numericalaperture of 0.63 and can operate at a spectral bandwidth of 300picometers, and preferably of 100 picometers, centered on 248.4nanometers. From the long conjugate end, it includes a firstquarter-wave plate 808, an object or reticle plane 110, a secondquarter-wave plate 811, a first lens group LG1, a folding mirror 820, asecond lens group LG2, a beamsplitter cube 830, a first quarter-waveplate 832, a concave mirror 834, a second quarter-wave plate 838, and athird lens group LG3. The image is formed at the image or wafer plane180.

[0120] The first lens group LG1 comprises a shell 812, a spaced doubletincluding a positive lens 814 and a negative lens 816, and a positivelens 818. The second lens group LG2 comprises a positive lens 822, aspaced doublet including a negative lens 824 and a positive lens 826,and a negative lens 828. The third lens group LG3 comprises two positivelenses 840 and 842, a shell 844, and two positive lenses 846 and 848.Again, as in the embodiment illustrated in FIG. 5, the folding mirror820 of FIG. 8 is not essential to the operation of the invention, butnevertheless permits the object 110 and image plane 180 to be parallelto each other which is convenient for the manufacture of semiconductordevices using photolithography.

[0121] The construction data of the fourth embodiment illustrated inFIG. 8 is given in Table 4 below. TABLE 4 Radius of Curvature Element(mm) Thickness Aperture Diameter (mm) Number Front Back (mm) Front BackGlass 808 Infinite Infinite 4.5000 122.0000 122.0000 Silica Space 2.0000110 Infinite 63.3853 Space 2.0000 811 Infinite Infinite 4.5000 122.0000122.0000 Silica 812 −183.5661 −215.7867CX 17.0000 122.8436 130.6579Silica Space 46.6205 814 −601.1535CC −230.9702CX 21.4839 149.1476153.3103 Silica Space 68.8075 816 −195.1255 −345.4510CX 15.0000 161.6789170.1025 Silica Space 3.0000 818 435.8058CX −1045.1785CX 24.9351177.4250 178.2672 Silica Space 130.0000 Decenter(1) 820 Infinite−64.5000 180.3457 Reflection 822 −210.7910CX 380.1625CX −43.1418181.6672 178.0170 Silica Space −15.8065 824 300.1724CC −123.4555CC−12.0000 166.7278 152.3101 Silica Space −3.8871 826 −126.8915CX972.6391CX −41.3263 154.8530 151.8327 Silica Space −1.5000 828−626.4905CX −116.6456CC −12.0000 147.6711 136.1163 Silica Space −31.8384830 Infinite Infinite −74.0000 137.2448 200.1127 Silica Decenter(2) 836Infinite 200.1128 Reflection 830 Infinite Infinite 74.0000 200.1127200.1127 Silica Space 2.0000 832 Infinite Infinite 6.0000 148.6188149.0707 Silica Space 14.4638 Stop 149.6392 834 Aspheric −14.4638149.6392 Reflection 832 Infinite Infinite −6.0000 144.8563 141.2737Silica Space −2.0000 830 Infinite Infinite −74.000 139.3606 117.3979Silica Decenter(3) 830 Infinite Infinite −61.000 117.3979 100.5074Silica Space −2.0000 838 Infinite Infinite −4.5000 99.6617 98.4157Silica Space −1.2000 840 −157.8776CX 2282.2178CX −13.7501 94.826791.8775 Silica Space −1.2000 842 −94.0059CX −46.6659CC −13.4850 82.866378.1418 Silica Space −1.2000 844 −147.2485CX −77.8924CC −22.2075 72.726250.6555 Silica Space −3.2091 846 −159.2880CX −519.4850CC −13.832149.5648 39.0473 Silica Space −0.2000 848 −129.3683CX −426.7350CC −6.150037.3816 32.4880 Silica Space Image Distance = −4.0000 850 Image infinite

[0122] The constants for the aspheric mirror 834 used in the equationlocated after Table 1 are as follows:

[0123] CURV=−0.00332614

[0124] K=0.000000

[0125] A=−4.32261E−10

[0126] B=3.50228E−14

[0127] C=7.13264E−19

[0128] D=2.73587E−22

[0129] This fourth embodiment is optimized for radiation centered on248.4 nm. The single refracting material of fused silica and the largeportion of refracting power restricts the spectral bandwidth of theembodiment depicted in FIG. 8. However, because the fourth embodimenthas a maximum numerical aperture of 0.63 rather than of 0.7 as in thefirst three embodiments, the fourth embodiment provides acceptableimaging over a spectral full-width-half-maximum bandwidth of 300picometers, or preferably of 100 picometers. Thus, in the former, anunnarrowed, or, in the latter, a narrowed excimer laser can be employedfor the illumination source.

[0130] The fourth embodiment differs from the first three embodiments inthat the net power of LG1 and LG2 of the fourth embodiment is weaklypositive rather than weakly negative as in the first three embodiments.In addition, this illustrates that the overall focal power of LG1 plusLG2 can be either positive or negative and still permit an infinitelydistant entrance pupil to be imaged at or near the concave mirror 834.

[0131]FIG. 9 illustrates a fifth embodiment of the optical reductionsystem of the present invention. Preferably, this embodiment has anumerical aperture of 0.60 and operates at a spectral bandwidth of 300picometers centered on 248.4 nanometers. From the long conjugate end, itincludes a first quarter-wave plate 908, an object or reticle plane 110,a second quarter-wave plate 911, a first lens group LG1, a foldingmirror 920, a second lens group LG2, a beamsplitter cube 930, a thirdquarter-wave plate 932, a concave mirror 934, a fourth quarter-waveplate 938, and a third lens group LG3. The image is formed at an imageor wafer plane 180.

[0132] The first lens group LG1 comprises a shell 912, a spaced doubletincluding a positive lens 914 and a negative lens 916, and a positivelens 918. The second lens group LG2 comprises a positive lens 922, aspaced doublet including a negative lens 924 and a positive lens 926,and a negative lens 928. The third lens group LG3 comprises two positivelenses 940 and 942, a shell 944, and two positive lenses 946 and 948.Again, as in the embodiment illustrated in FIG. 5, the folding mirror920 of FIG. 9 is not essential to the operation of the invention, butnevetheless permits the object and image planes to be parallel to eachother which is convenient for the manufacture of semiconductor devicesusing photolithography.

[0133] The construction data of the fifth embodiment illustrated in FIG.9 is given in Table 5 below. TABLE 5 Radius of Curvature Element (mm)Thickness Aperture Diameter (mm) Number Front Back (mm) Front Back Glass908 Infinite Infinite −4.4550 120.0000 120.0000 Silica Space 1.1880 910Infinite 62.7514 Space 1.1880 911 Infinite Infinite −4.4550 120.0000120.0000 Silica 912 −136.1154 CC −152.5295 CX 16.8300 120.7552 129.4354Silica Space 4.5206 914 −270.1396 CC −191.8742 CX 20.5341 132.9152139.0377 Silica Space 90.8476 916 −188.9000 CC −284.7476 CX 17.5000156.1938 165.6567 Silica Space 2.9700 918   433.8174 CX −841.5599CX25.8293 173.8279 174.8334 Silica Space 149.4549 Decenter(1) 920 Infinite−61.0000 177.2183 Reflection 922 −190.3251 CX −8413.4836 CC −34.4584178.5071 174.2260 Silica Space −51.5487 924 690.5706 CC −146.4997 CC−11.8800 150.4109 141.8021 Silica Space −10.6267 526 −265.9886 CX1773.5314CX −24.1851 142.1851 141.2400 Silica Space −1.5000 928−244.9899 CX −142.8558 CC −11.8800 139.3290 133.8967 Silica Space−21.6411 930 Infinite Infinite −71.2800 134.3115 189.7826 SilicaDecenter(2) 936 Infinite 189.7826 Reflection 930 Infinite Infinite71.2800 189.7826 189.7826 Silica Space 1.9800 932 Infinite Infinite5.9400 142.3429 142.6707 Silica Space 18.5263 Stop 143.5034 934 Aspheric−18.5263 143.5034 Reflection 932 Infinite Infinite −5.9400 134.2788130.9398 Silica Space −1.9800 930 Infinite Infinite −71.2800 130.1221111.7247 Silica Decenter (3) 930 Infinite Infinite −60.4000 111.724796.1353 Silica Space −1.9800 938 Infinite Infinite −4.4550 95.356294.2064 Silica Space −1.1880 940 −127.4561 CX. −1398.8019CC −13.010490.4737 87.7002 Silica Space −1.1880 942 −98.8795 CX −424.1302 CC−12.2874 80.7016 76.3270 Silica Space −1.1880 944 −132.0104 CX −70.9574CC −17.8706 71.0789 53.4306 Silica Space −3.1246 946 −123.1071 CX−585.4471 CC −19.9496 52.6417 38.2256 Silica Space −0.1980 948 −137.8349CX −292.6179 CX −6.0885 36.7251 31.8484 Silica Space Image Distance =−4.0000 950 Image Infinite 26.5000

[0134] The constants for the aspheric mirror 934 used in the equationlocated after table 1 are as follows:

[0135] CURV=−0.00325995

[0136] K=0.000000

[0137] A=−6.91799E−10

[0138] B=5.26952E−15

[0139] C=6.10046E−19

[0140] D=1.59429E−22

[0141] This fifth embodiment is optimized for radiation centered on248.4 nm. THE single refracting material of fused silica and the largeportion of refracting power restricts the spectral bandwidth of theembodiment depicted in FIG. 9. However, because the fifth embodiment hasa maximum numerical aperture of 0.6 rather than of 0.7 as in the firstthree embodiments, the fifth embodiment provides acceptable imaging overa spectral full-width-half-maximum bandwidth of 300 picometers. Thus, anunnarrowed excimer laser can be employed for an illumination source. Thefifth embodiment differs from the first three embodiments in that thenet power of LG1 and LG2 of the fifth embodiment is weakly positiverather than weakly negative as in the first three embodiments. Inaddition, this illustrates that the overall focal power of LG1 plus LG2can be either positive or negative and still permit an infinitelydistant entrance pupil to be imaged at or near the concave mirror 934.

[0142] IV. Alternate Implementation

[0143] It is apparent to one skilled in the relevant art that the use ofthe first quarter-wave plate in any of the above embodiments depends onthe initial polarization of the radiation incident on the long conjugateend. Therefore, if the polarization of the light is circular orunpolarized prior to the long conjugate end, then the first quarter-waveplate, used to transform linearly polarized light into circularlypolarized light, could be omitted.

[0144] Such an implementation can be shown by omitting firstquarter-wave plate 305 from FIG. 3 and/or first quarter-wave plate 405from FIG. 4. Further implementations of this configuration in the otherembodiments described above are obvious to one skilled in the relevantart.

CONCLUSION

[0145] While specific embodiments of the present invention have beendescribed above, it should be understood that they have been presentedby way of example only, and not limitation. It will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined in the appended claims. Thus, the breadth and scopeof the present invention should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

What is claimed is:
 1. An optical reduction system having an objectspace numerical aperture comprising: first phase shifting means forproviding a quarter wavelength phase difference; an object means forproviding a projected image, wherein the phase difference of said firstphase shifting means provides circularly polarized light, and the imageprojected from said object means provides image details using samecircularly polarized light; and second phase shifting means forproviding a quarter wavelength phase difference.
 2. The opticalreduction system of claim 1, further comprising: first lens means forproviding a negative power having an emerging numerical aperture, theemerging numerical aperture being larger than the object space numericalaperture; a beamsplitter; a concave mirror; and second lens means forproviding a positive power, wherein the phase difference of said phaseshifting means provides linearly polarized light, the negative power ofsaid first lens means provides enough power to image an entrance pupilof the system at infinity to an aperture stop at or near said mirror,and the positive power of said second lens means provides substantiallyall of the power of the system and images the exit pupil of the systemto infinity.
 3. An optical reduction system from the long conjugate endto the short conjugate end, comprising: a first quarter-wave plate; anobject plane; a second quarter-wave plate; a first lens group ofpositive power, said first lens group having an entering numericalaperture; a second lens group of negative power, said second lens groupseparated from said first lens group and having an emerging numericalaperture greater than the entering numerical aperture of said first lensgroup; a beamsplitter; a quarter-wave plate; a concave mirror; a thirdlens group of positive power; and wherein the positive power of saidfirst lens group provides enough power to image an entrance pupil of thesystem at infinity through said second lens group to an aperture stop ator near said mirror, the negative power of said second lens groupprovides the necessary conjugates for said concave mirror, and thepositive power of said third lens group provides the remainder of thetotal system power and images the exit pupil of the system to infinity.4. The optical reduction system as in claim 3 wherein: said secondquarter-wave plate can be anywhere before said beamsplitter.
 5. Theoptical reduction system as in claim 4, further comprising: a thirdquarter-wave plate placed between said beamsplitter and said concavemirror.
 6. The optical reduction system as in claim 5, furthercomprising: a fourth quarter-wave plate placed between said beamsplitterand said third lens group.
 7. An optical reduction system from the longconjugate end to the short conjugate end, comprising: a firstquarter-wave plate; a first lens group of positive power; a second lensgroup of negative power; a beamsplitter; a second quarter-wave plate; aconcave mirror; a third lens group of positive power; said first lensgroup including, at least one lens of positive power; a first lens ofsubstantially zero power; and a first doublet, whereby said first lensof substantially zero power and said first doublet help correctaberrations such as astigmatism, field curvature, and distortion, saidsecond lens group including, at least one lens of negative power; apositive lens; and a second doublet, whereby said at least one lens ofnegative power provides a diverging beam for said beamsplitter and saidmirror, said positive lens provides lateral color correction, and saidsecond doublet helps to correct for spherical aberration and coma, andwherein the positive power of said first lens group provides enoughpower to image the entrance pupil of the system at infinity through saidsecond lens group to an aperture stop at or near said mirror, thenegative power of said second lens group provides the necessaryconjugates for said concave mirror, and the positive power of said thirdlens group provides the remainder of the total system power and imagesthe exit pupil of the system to infinity.
 8. The optical reductionsystem as in claim 7, further comprising: a third quarter-wave plateplaced between said beamsplitter and said third lens group.
 9. Theoptical reduction system as in claim 8, further comprising: a fourthquarter-wave plate placed before the optical reduction system; wherebylinearly polarized radiation incident upon the system is circularlypolarized.
 10. An optical reduction system comprising: a constructionaccording to the following construction data TABLE 1 Radius of CurvatureElement (mm) Thickness Aperture Diameter (mm) Number Front Back (mm)Front Back Glass 508 Infinite Infinite 4.500 123.0000 123.0000 SilicaSpace 0.7500 110 Infinite 63.3853 Space 0.7500 511 Infinite Infinite4.500 123.0000 123.0000 Silica Space 0.7500 512 −158.7745 −177.888015.0000 124.0478 131.7725 Silica Space 36.1130 514 −556.6911 −202.007222.2126 148.3881 152.5669 Silica Space 38.7188 516 −183.7199 −558.880315.0000 156.5546 166.5750 Silica Space 10.0674 518 427.2527 −612.245028.8010 177.4010 179.0292 Silica Space 132.3320 520 Infinite −74.0000184.6402 Reflection 522 −240.4810 2050.9592 −33.3135 188.4055 185.3395Silica Space −29.3434 524 421.7829 −145.6176 −12.0000 175.5823 169.0234Silica Space −4.2326 526 −150.4759 472.0653 −46.5091 171.4244 169.9587Silica Space −2.0000 528 −1472.2790 −138.2223 −15.0000 165.3586 154.8084Silica Space −27.2060 530 Infinite Infinite −91.8186 155.6662 253.0917Silica 536 Infinite 253.0917 Reflection 530 Infinite Infinite 91.8186253.0917 253.0917 Silica Space 2.0000 532 Infinite Infinite 6.0000185.8693 186.8401 Silica Space 17.9918 Stop 188.0655 534 Aspheric−17.9918 188.0655 Reflection 532 Infinite Infinite −6.0000 183.5471180.1419 Silica Space −2.0000 530 Infinite Infinite −91.8186 178.3346149.2832 Silica 530 Infinite Infinite −70.000 149.2832 128.8604 SilicaSpace −2.0000 538 Infinite Infinite −4.500 127.9681 126.6552 SilicaSpace −0.7500 540 −175.1330 1737.4442 −17.7754 121.4715 118.2689 SilicaSpace −0.7500 542 −108.8178 −580.1370 −18.2407 104.5228 97.7967 SilicaSpace −0.7500 544 −202.2637 −86.6025 −31.1216 91.7061 57.4968 SilicaSpace −2.3507 546 −122.1235 −488.7122 −17.9476 56.4818 41.1675 SilicaSpace −0.2000 548 −160.8506 −360.1907 −6.1500 39.4528 33.5764 SilicaSpace −4.000 180 Infinite 26.5019


11. An optical reduction system having a relatively high numericalaperture, from the long conjugate end to the short conjugate end,comprising: an object plane; a first quarter-wave plate; a firstdoublet; a first positive lens; a second positive lens; a shell; afolding mirror; a third positive lens; a first negative lens; a forthpositive lens; a second negative lens; a beamsplitter cube; a secondquarter-wave plate; a concave mirror; a third quarter-wave plate; afifth positive lens; a second doublet; a sixth positive lens; and athird doublet, arranged such that radiation entering the system passesthrough said object plane, said first quarter-wave plate, said firstdoublet, said first positive lens, said second positive lens, saidshell, said folding mirror, said third positive lens, said firstnegative lens, said second negative lens; said beamsplitter cube, saidsecond quarter-wave plate, and is reflected by said concave mirror backthrough said second quarter-wave plate and said beamsplitter cube, andthrough said third quarter-wave plate, said fifth positive lens, saidsecond doublet; said sixth positive lens, and said third doublet. 12.The optical reduction system as in claim 11 wherein: said firstquarter-wave plate can be anywhere before said beamsplitter.
 13. Theoptical reduction system as in claim 12, further comprising: a fourthquarter-wave plate before said object plane.
 14. The optical reductionsystem as in claim 13 having: a construction according to the followingconstruction data TABLE 2 Radius Element of Curvature (mm) ThicknessAperture Diameter (mm) Number Front Back (mm) Front Back Glass 608Infinite Infinite 4.5000 123.0000 123.0000 Silica Space 0.5000 110Infinite 60.4852 Space 0.5000 611 Infinite Infinite 4.5000 123.0000123.0000 Silica 612 −205.5158 539.1791 15.2158 124.0926 137.3346 SilicaSpace 8.8054 614 2080.9700 −210.6539 32.4984 142.6149 151.7878 SilicaSpace 1.2676 616 310.4463 700.3748 40.7304 162.4908 165.2126 CaFl Space0.5000 618 634.1820 −798.8523 27.5892 165.4595 166.4747 Silica Space0.5000 620 1480.0597 1312.1247 25.4322 168.7516 164.7651 Silica Space136.2343 622 Infinite −74.0000 161.9590 Reflection 624 −761.91761088.9351 −19.2150 160.3165 159.2384 Silica Space −19.9465 626 648.8361−202.5872 −12.0000 155.1711 153.0635 CaFl Space −7.6304 628 −400.4276458.5060 −25.8769 153.0635 153.8055 Silica Space −2.0000 630 −818.0922−168.5034 −27.5927 152.6663 147.5200 CaFl Space −20.5014 632 InfiniteInfinite −91.7553 148.6158 252.7349 Silica 638 Infinite 252.7349Reflection 632 Infinite Infinite 91.7553 252.7349 252.7349 Silica Space2.0000 634 Infinite Infinite 6.0000 185.8070 187.0026 Silica Space18.1636 Stop 188.5681 636 Aspheric −18.1636 188.5681 Reflection 634Infinite Infinite −6.0000 184.2566 181.1084 Silica Space −2.0000 632Infinite Infinite −91.7553 179.3838 151.7747 Silica 632 InfiniteInfinite −70.0000 151.7747 133.3985 Silica Space −2.0000 640 InfiniteInfinite −4.5000 132.5690 131.3876 Silica Space −0.5000 642 −112.0665−597.6805 −21.4866 123.4895 119.2442 Silica Space −0.5000 644 −116.3137282.3140 −24.0940 107.8451 101.2412 CaFl 646 282.3140 −66.5293 −13.7306101.2412 72.6862 Silica Space −2.6346 648 −77.2627 −374.4800 −17.959472.0749 62.7659 Silica Space −0.5452 650 −130.1381 −57.1295 −20.814758.9696 37.4889 Silica 652 −57.1295 −7305.8777 −6.1425 37.4889 34.3156CaFl Space −4.0000 180 Infinite 26.4992


15. An optical reduction system having a relatively high numericalaperture, from the long conjugate end to the short conjugate end,comprising: an object plane; a first quarter-wave plate; a firstdoublet; a second doublet; a first positive lens; a folding mirror; asecond positive lens; a first negative lens; a third positive lens; asecond negative lens; a beamsplitter cube; a second quarter-wave plate;a concave mirror; a third quarter-wave plate; a fourth positive lens; athird doublet; a fifth positive lens; a shell; and a sixth positivelens, arranged such that radiation entering the system passes throughsaid object plane, said first quarter-wave plate, said first doublet,said second doublet, said first positive lens, said folding mirror, saidsecond positive lens, said first negative lens, said third positivelens, said second negative lens, said beamsplitter cube, said secondquarter-wave plate, and is reflected by said concave mirror back throughsaid second quarter-wave plate and said beamsplitter cube, and throughsaid third quarter-wave plate, said fourth positive lens, said thirddoublet, said fifth positive lens, said shell, and said sixth positivelens.
 16. The optical reduction system as in claim 15 wherein: saidfirst quarter-wave plate can be anywhere before said beamsplitter. 17.An optical reduction system as in claim 16 further comprising: a fourthquarter-wave plate before said object plane.
 18. The optical reductionsystem as in claim 17 having: a construction according to the followingconstruction data TABLE 3 Radius Element of Curvature (mm) ThicknessAperture Diameter (mm) Number Front Back (mm) Front Back Glass 708Infinite Infinite 4.5000 125.0000 125.0000 Silica Space 0.5000 110Infinite 59.2960 Space 0.5000 711 Infinite Infinite 4.5000 125.0000125.0000 Silica 712 −620.7809 361.8305 20.2974 125.9406 134.7227 PBM2YSpace 2.6174 714 515.7935 −455.1015 39.8858 135.3384 145.6015 PBM2YSpace 14.7197 716 431.3189 −239.4002 36.9329 155.6269 157.3014 BSL7YSpace 0.5000 718 −259.6013 685.3286 26.3534 156.9363 162.2451 PBM2YSpace 1.4303 720 361.5709 −1853.2955 23.3934 168.7516 165.1801 BAL15YSpace 131.8538 722 Infinite −77.8469 169.9390 Reflection 724 −429.2950455.4247 −32.3086 173.0235 171.1102 PBL6Y Space −27.6206 726 401.0363−180.0031 −12.0000 159.3555 154.7155 BSL7Y Space −5.6227 728 −258.47221301.3764 −26.1321 154.7155 154.1517 PBM8Y Space −2.0000 730 −1282.8931−180.2226 −12.0000 153.1461 149.4794 BSL7Y Space −19.7282 732 InfiniteInfinite −91.7349 150.4585 252.6772 Silica 738 Infinite 252.6772Reflection 732 Infinite Infinite 91.7349 252.6772 252.6772 Silica Space2.0000 734 Infinite Infinite 6.0000 185.6435 186.7758 Silica Space18.2715 Stop 188.1745 736 Aspheric −18.2715 188.1745 Reflection 734Infinite Infinite −6.0000 183.6393 180.1377 Silica Space −2.0000 732Infinite Infinite −91.7349 178.3236 147.9888 Silica 732 InfiniteInfinite −70.0000 147.9888 126.9282 Silica Space −2.000 740 InfiniteInfinite −4.5000 126.0289 124.6750 Silica Space −0.5000 742 −119.8912−610.6840 −18.6508 117.5305 113.4233 BSM51Y Space −0.5000 744 −114.1327384.9135 −21.1139 102.6172 96.4137 BSL7Y 746 384.9135 −70.2077 −13.057696.4137 71.1691 PBL26Y Space −2.8552 748 −85.7858 −400.3240 −16.914770.5182 61.2633 BSM51Y Space −0.8180 750 −151.5235 −54.0114 −19.581057.6234 37.3909 BSM51Y 752 −54.0114 −2011.1057 −6.3947 37.3909 34.2119PBL6Y Space −4.0000 180 Infinite 26.5002


19. An optical reduction system having a relatively high numericalaperture, from the long conjugate end to the short conjugate end,comprising: an object plane; a first lens group of positive power; asecond lens group of negative power; a beamsplitter; a concave mirror; athird lens group of positive power; a first quarter-wave plate placedbefore said object plane; a second quarter-wave plate placed betweensaid object plane and said first lens group; a third quarter-wave plateplaced between said beamsplitter and said concave mirror; a fourthquarter-wave plate placed between said beamsplitter and said third lensgroup; and wherein the properties of said first quarter-wave platecircularly polarize the linearly polarized radiation entering thesystem, and the properties of said second quarter-wave plate linearlypolarize the circularly polarized radiation leaving said object plane.20. The optical reduction system as in claim 19 wherein: the firstquarter-wave plate is zero order quarter-wave plate.
 21. The opticalreduction system as in claim 19 wherein: the second quarter-wave plateis a zero order quarter-wave plate.
 22. An optical reduction systemhaving a relatively high numerical aperture, from the long conjugate endto the short conjugate end, comprising: a first quarter-wave plate; anobject plane; a second quarter-wave plate; a first lens group ofpositive power; a second lens group of negative power, said first andsecond lens group having a net power; a beamsplitter, the net power ofsaid first and second lens group resulting in a non-collimated beamentering said beamsplitter from said first and second lens group; athird quarter-wave plate; a concave mirror, the net power of said firstand second lens group providing only enough power to image the systementrance pupil at infinity to an aperture stop at or near said concavemirror; a fourth quarter-wave plate; and a third lens group of positivepower; arranged such that radiation entering said system passes throughsaid first lens group, said second lens group, said beamsplitter, and isreflected by said concave mirror back through said beamsplitter andthrough said third lens group.
 23. The optical reduction system as inclaim 22 wherein: said first quarter-wave plate is oriented with theinput light, said second and said fourth quarter-wave plates are placedin parallel orientation with one another, and said third quarter-waveplate is placed perpendicular to said second quarter-wave plate.
 24. Theoptical reduction system as in claim 23 having a construction accordingto the following data TABLE 4 Radius Element of Curvature (mm) ThicknessAperture Diameter (mm) Number Front Back (mm) Front Back Glass 808Infinite Infinite 4.5000 122.0000 122.0000 Silica Space 2.0000 110Infinite 63.3853 Space 2.0000 811 Infinite Infinite 4.5000 122.0000122.0000 Silica 812 −183.5661 −215.7867CX 17.0000 122.8436 130.6579Silica Space 46.6205 814 −601.1535CC −230.9702CX 21.4839 149.1476153.3103 Silica Space 68.8075 816 −195.1255 −345.4510CX 15.0000 161.6789170.1025 Silica Space 3.0000 818 435.8058CX −1045.1785CX 24.9351177.4250 178.2672 Silica Space 130.0000 Decenter(1) 820 Infinite−64.5000 180.3457 Reflection 822 −210.7910CX 380.1625CX −43.1418181.6672 178.0170 Silica Space −15.8065 824 300.1724CC −123.4555CC−12.0000 166.7278 152.3101 Silica Space −3.8871 826 −126.8915CX972.6391CX −41.3263 154.8530 151.8327 Silica Space −1.5000 828−626.4905CX −116.6456CC −12.0000 147.6711 136.1163 Silica Space −31.8384830 Infinite Infinite −74.0000 137.2448 200.1127 Silica Decenter(2)| 836Infinite 200.1128 Reflection 830 Infinite Infinite 74.0000 200.1127200.1127 Silica Space 2.0000 832 Infinite Infinite 6.0000 148.6188149.0707 Silica Space 14.4638 Stop 149.6392 834 Aspheric −14.4638149.6392 Reflection 832 Infinite Infinite −6.0000 144.8563 141.2737Silica Space −2.0000 830 Infinite Infinite −74.000 139.3606 117.3979Silica Decenter(3) 830 Infinite Infinite −61.000 117.3979 100.5074Silica Space −2.0000 838 Infinite Infinite −4.5000 99.6617 98.4157Silica Space −1.2000 840 −157.8776CX 2282.2178CX −13.7501 94.826791.8775 Silica Space −1.2000 842 −94.0059CX −46.6659CC −13.4850 82.866378.1418 Silica Space −1.2000 844 −147.2485CX −77.8924CC −22.2075 72.726250.6555 Silica Space −3.2091 846 −159.2880CX −519.4850CC −13.832149.5648 39.0473 Silica Space −0.2000 848 −129.3683CX −426.7350CC −6.150037.3816 32.4880 Silica Space Image Distance = −4.0000 850 Image Infinite


25. The optical reduction system as in claim 23 having a constructionaccording to the following data TABLE 5 Radius Element of Curvature (mm)Thickness Aperture Diameter (mm) Number Front Back (mm) Front Back Glass908 Infinite Infinite −4.4550 120.0000 120.0000 Silica Space 1.1880 910Infinite 62.7514 Space 1.1880 911 Infinite Infinite −4.4550 120.0000120.0000 Silica 912 −136.1154 CC −152.5295 CX 16.8300 120.7552 129.4354Silica Space 4.5206 914 −270.1396 CC −191.8742 CX 20.5341 132.9152139.0377 Silica Space 90.8476 916 −188.9000 CC −284.7476 CX 17.5000156.1938 165.6567 Silica Space 2.9700 918 433.8174 CX −841.5599 CX25.8293 173.8279 174.8334 Silica Space 149.4549 Decenter(1) 920 Infinite−61.0000 177.2183 Reflection 922 −190.3251 CX −8413.4836 CC −34.4584178.5071 174.2260 Silica Space −51.5487 924 690.5706 CC −146.4997 CC−11.8800 150.4109 141.8021 Silica Space −10.6267 526 −265.9886 CX1773.5314CX −24.1851 142.1851 141.2400 Silica Space −1.5000 928−244.9899 CX −142.8558 CC −11.8800 139.3290 133.8967 Silica Space−21.6411 930 Infinite Infinite −71.2800 134.3115 189.7826 SilicaDecenter(2) 936 Infinite 189.7826 Reflection 930 Infinite Infinite71.2800 189.7826 189.7826 Silica Space 1.9800 932 Infinite Infinite5.9400 142.3429 142.6707 Silica Space 18.5263 Stop 143.5034 934 Aspheric−18.5263 143.5034 Reflection 932 Infinite Infinite −5.9400 134.2788130.9398 Silica Space −1.9800 930 Infinite Infinite −71.2800 130.1221111.7247 Silica Decenter (3) 930 Infinite Infinite −60.4000 111.724796.1353 Silica Space −1.9800 938 Infinite Infinite −4.4550 95.356294.2064 Silica Space −1.1880 940 −127.4561 CX −1398.8019CC −13.010490.4737 87.7002 Silica Space −1.1880 942 −98.8795 CX −424.1302 CC−12.2874 80.7016 76.3270 Silica Space −1.1880 944 −132.0104 CX −70.9574CC −17.8706 71.0789 53.4306 Silica Space −3.1246 946 −123.1071 CX−585.4471 CC −19.9496 52.6417 38.2256 Silica Space −0.1980 948 −137.8349CX −292.6179 CX −6.0885 36.7251 31.8484 Silica Space Image Distance =−4.0000 950 Image Infinite 26.5000


26. An optical reduction system having an image space numerical apertureand an object space numerical aperture, from the long conjugate end tothe short conjugate end, comprising: a first lens group of positivepower; a second lens group of negative power, said second lens grouphaving an emerging numerical aperture, the emerging numerical aperturebeing substantially similar to the object space numerical aperture; abeamsplitter; a concave mirror; and a third lens group of positivepower; arranged such that radiation entering said system passes throughsaid first lens group, said second lens group, said beamsplitter, and isreflected by said concave mirror back through said beamsplitter andthrough said third lens group.
 27. The optical reduction system as inclaim 26 wherein: the emerging numerical aperture is slightly largerthan the object space numerical aperture.